The nerve growth factor is a polypeptide hormone-like substance that is required for the normal growth and development of sympathetic and embryonic sensory neurons (possibly other cell types). The long term goals of this research are to understand the mechanism of action of the nerve growth factor. Once the mechanism of action of the nerve growth factor is fully understood, a better understanding of how normal nerve tissue grows and develops will be had. This will lead to a greater chance of correcting the abnormal functioning of the nervous system (such as in the case of inducing injured nervous tissue to regenerate). At the present time, it is known that the first step in the action of the nerve growth factor is its binding to a cell surface membrane receptor on responsive cells. Unfortunately, understanding the equilibrium and kinetic characteristics of the interaction of the nerve growth factor with its receptor has not uncovered the mechanism of action of the nerve growth factor. The present proposal is taking a different approach. It appears that the type I nerve growth factor receptor may be a serine protease and/or esterase. The nerve growth factor receptors (both the type I and type II receptors) will be isolated and purified using lentil lectin affinity chromatography, nerve growth factor affinity chromatography, and high performance liquid chromatography (both size exclusion and ion exchange). After the type I receptor is purified, the enzyme specificity will be investigated using various synthetic substrates. The number of reactive serines per type I receptor molecule will be determined using phenylmethylsulfonyl fluoride. The effects that the nerve growth factor has on the enzymatic activity will be determined. The relationship between the sulfhydryl group on the type I receptor and the reactive serine will be determined using radioactive N-ethylmaleimide and radioactive phenylmethylsulfonyl fluoride. The type II receptor doesn't appear to contain either the reactive serine or the sulfhydryl group. Since this receptor will also be purified, the presence of these groups will be directly determined using the same techniques that were used for the type I receptor. Finally, peptide maps of the type I and the type II nerve growth factor receptors will be obtained. The peptide maps for the two receptors will be compared to determine if there is a sequence homology between the type I and type II receptors.